In a magnetic tape recorder which may store and reproduce information by helical scanning, it is common to provide a cylinder, having a rotary head, inclining to a horizontal reference plane (for example, a top surface of a chassis) which is perpendicular to rotational axes of tape reels. When such a cylinder is utilized, a pair of tape pull-out means are required to pull out a tape from a tape cassette and to wind the tape around the cylinder for a predetermined angle (hereinafter this operation will be called a tape-loading operation).
In this connection, it has been known that when a tape is transferred by keeping the tape surfaces orthogonal to a reference plane and at the same time by keeping the tape edges parallel to the reference plane, and is contacted with a cylinder surface which is inclined to said reference plane, the orientation of the surfaces and edges of said tape with respect to the reference plane are varied.
There is a known tape pull-out means which has two guide pins, one is inclined and the other is oriented orthogonal to a reference plane, mounted on a carrier movable between a home position adjacent to a tape reel and a pulled-out position or a loading position adjacent to a cylinder. More particularly, the inclined pins may change the orientation of the surfaces and edges of said tape with respect to the reference plane upstream and downstream of said cylinder so that the tape surfaces orthogonal to said reference plane are changed into nonorthogonal (in upstream position) or vice versa (downstream) and that tape edges which are parallel to the reference plane are changed into nonparallel (upstream) or vice versa (downstream). When the pull-out means are moved, however, the inclined guide pins are contacted with the tape surfaces, and a force to move the tape in the direction of its width is generated. This force may cause a shift of the tape, and movement of the tape away from the cylinder may result in a failure to pull out the tape.
A tape pull-out means having a plurality of inclined pins is disclosed in Japanese Unexamined Patent Application Gazette No. 60(1985)-253053. The use of a plurality of inclined pins necessitates accurate adjustment of relative inclination between the pins and the associated cylinder in manufacturing and installation. In order to reduce the troublesome adjustment of the relative inclination, it is proposed, in this reference, to form two inclined pins in one block.
However, the tape pull-out means having one or more inclined pins on a movable carrier has the defect of requiring accurate installation and positioning at their pulled-out positions. Inaccuracy in installation or positioning may result in inaccuracy in winding the tape on the inclining pin for a predetermined angle which in turn results in inaccuracy of the angle between the tape surface and a reference plane, and inaccuracy of the distance between the tape edges and the reference plane. This problem cannot be solved even if guide blocks each having one or more inclined pins are fixedly disposed in close proximity of a cylinder as a stationary guides, since inaccuracy of the positions of the pull-out pins may result in inaccuracy in winding the tape on said inclined pin in desired angles.
The solution of this problem is disclosed in the U.S. patent application Ser. No. 154,265 filed on Feb. 10, 1988 now U.S. Pat. No. 4,875,126, by Niro Nakamichi and assigned to the same assignee of the present invention. In this application, there is disclosed a stationary tape guide having a laterally extending guide path, the general contour of which is forwardly convexed on a projection on a horizontal reference plane. At least two straight guide projections are inclined to said reference plane and a single straight guide projection extending orthogonal to said reference plane is serially and integrally provided on a guide block. In the preferred embodiments in said application, the tape guide is further provided with means for guiding the upper edge of a tape integrally or detachably therewith.
In Japanese Utility model Application No. 62(1987)-175168 which was filed by the same assignee of the present application on Nov. 17, 1987, a stationary tape guide having a tape-edge guide which determines the level of the guide surface is disclosed.
The tape guide disclosed in the application may adequately operate, however, a tape wound along an inclined cylinder tends to shift in its axial direction in operation due to the inclination of the cylinder. This tendency is increased when a tape is transferred on a wet or moisturized surface of an inclined cylinder rotating in operation or on a surface of an inclined cylinder non-rotated in malfunction of magnetic tape recorder. When the tape is axially shifted and rides on or leaves off the tape-edge guide, the tape is damaged.